What are MCLs and HALs?
The purity of drinking water is often expressed with two government standards: Maximum Contaminant Levels, and Health Advisory Levels. Maximum Contaminant Levels (MCLs), also known as primary standards, represent the maximum permissible level of a contaminant in public drinking water. MCLs are derived from scientific studies on health risks associated with long-term ingestion of certain contaminants in drinking water. MCLs are legally enforceable for public water supplies. If an MCL is exceeded in water, a supplier must notify its customers and act to reduce the contaminant levels to comply with MCL standards. MCls are established for many pesticides that can be removed effectively and economically from water supplies. Health Advisories Levels (HALs) are similar to MCLs, but only the potential health concerns for certain contaminants in drinking water are considered. Health Advisory Levels are not legally enforceable and serve only as health risk advisory guidelines. HALs may be set fo
